DE69103919T2 - Diamino compounds and precursors therefor. - Google Patents

Description

The invention relates to novel diamino compounds and intermediates used in their preparation. In particular, it relates to novel diamino compounds which can be used as a raw material for an orienting polyimide film with a high pretilt angle in a liquid crystal display element, and to dinitro compounds and diol compounds which are used as intermediates in the preparation of the above-mentioned diamino compounds.

As liquid crystal display elements for watches, electronic calculators, etc., twisted nematic (abbreviated to "TN") display systems having a structure in which the orientation direction of nematic liquid crystal molecules is twisted by 90º between a pair of upper and lower electrode substrates are currently mainly used. However, when this display system is subjected to a high-load drive, the contrast becomes poor and the viewing angle becomes narrow; therefore, it has not been sufficient to improve the display quality and the display surface. Recently, a liquid crystal display making use of a super-twisted birefringence effect has been reported (TJ Scheffer and J. Nethring, Appl. Phys. Lett., 45 (10), 1021 (1984)). Since then, a liquid crystal cell (abbreviated to "STN") has been developed which makes use of a super-twisted nematic system in which the orientation direction of the nematic liquid crystal molecules between the upper and lower electrodes is twisted by 180º to 300º; thus, even in the case of a liquid crystal display element providing a large image surface, liquid crystal displays with a satisfactory display quality can be obtained. In the case of a liquid crystal cell used for such elements, In the case of the orientation film, it is necessary to create a certain angle (hereinafter abbreviated to "pretilt angle") between the substrate planes and the liquid crystal molecules in order not only to orient the liquid crystal molecules but also to improve the response characteristics and ensure the bistability. In addition, it is preferable that the larger the twist angle, the larger the pretilt angle. In the case of those elements having a relatively small twist angle (180º to 200º twist), the interface treatment on the electrode substrates is sufficient if the cell is provided with an orientation film having an interface with a currently generally used pretilt angle (abbreviated to "Θ") of 5º or less. In the case of those elements having a system with a twist angle of 200º to 300º, in which they have a better display quality, however, it is necessary to use an interface with a larger pretilt angle (5º <Θ≤30º); Thus, a liquid crystal display cell is required which is provided with an orienting film which satisfies such a pretilt angle.

In the case of the currently used polyamide orientation films for a TN cell, commercially available display cells have a pretilt angle limited to 5º.

Polyimide orientation films with a large pretilt angle for STN cells also exist, but they still have a problem in terms of stability and reproducibility of a pretilt angle over the entire range of cell substrates having a wide display area. In order to obtain a large pretilt angle with certainty, the best method at present is to form a thin film of SiO₂, etc. by oblique-angle vacuum deposition. However, the formation of such a thin film by vacuum deposition, when carried out in the form of industrial mass production, is disadvantageous in terms of the cost of the device required for the production. There is therefore a serious need to develop a Orientation and a large pretilt angle through an interfacial treatment by rubbing a thin film of an organic substance according to the same process used in the conventional TN cell, thus creating stability and reproducibility of the pretilt angle.

Japanese Patent Application Laid-Open No. Sho 61-240223 describes a liquid crystal display element provided with a liquid crystal alignment film using a polyimide resin containing repeating units of the formula

having.

The raw material for the unit is also a concrete example of a diamine of the formula

described therein.

However, the polyimide alignment film obtained by using this diamino compound has a disadvantage in that a large pretilt angle is not obtained, as shown in the comparative example mentioned later. Therefore, a new diamino compound which can be used as a starting material for organic alignment films is desired.

The object of the invention is to solve the problems described above and to provide a novel diamino compound as a starting material for an orientation film made of organic substances, with which superior orientation properties and a uniform and large pretilt angle can be achieved by rubbing, as well as to provide intermediates for the diamino compound.

The invention therefore firstly relates to a diamino compound of the formula

Secondly, the invention relates to a dinitro compound of the formula

Finally, the invention relates to a diol compound of the formula

In the above formulas (1), (2) and (3), R₁ to R₆ each represent a hydrogen atom or an alkyl group having 1 to 22 carbon atoms, where these radicals may be the same or different, and R₇ to R₁₄ each represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, where these radicals may be the same or different.

Specific examples of the diamino compound according to the invention are:

1,1-bis[4-(4-aminophenoxy)phenyl)-4-(2-cyclohexylethyl)- cyclohexane

1,1-bisp[4-(4-aminophenoxy)phenyl)-4-[2-(trans-4-methylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-ethylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-propylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[trans-4-n-butylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl)-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-trans-4-n-hexylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-heptylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-octylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-nonylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-decylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-undecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-dodecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl)-4-[2-(trans-4-n-tridecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl)-4-[2-(trans-4-n-tetradecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-pentadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-hexadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-heptadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-octadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-nonadecylcyclohexyl)ethyl]cyclohexane

Specific examples of the dinitro compound according to the invention are:

1,1-bis[4-(4-nitrophenoxy)phenyl)-4-(2-cyclohexylethyl)- cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-methylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-ethylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-propylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl)-4-[2-(trans-4-n-butylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-hexylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-heptylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(nitrophenoxy)phenyl)-4-(2-(trans-4-n-octylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-nonylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-decylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-undecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-dodecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-tridecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-tetradecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-pentadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-hexadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-heptadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-octadecylcyclohexyl)ethyl]cyclohexane

1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-(trans-4-n-nonadecylcyclohexyl)ethyl]cyclohexane

Specific examples of the diol compound according to the invention are:

1,1-bis(4-hydroxyphenyl)-4-(2-cyclohexylethyl)cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-methylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-ethylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-propylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-butylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-pentylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-hexylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-heptylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-octylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-nonylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-decylcyclohexyl)- ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-undecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-dodecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-tridecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-tetradecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-pentadecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-hexadecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-heptadecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-octadecylcyclohexyl)ethyl]cyclohexane

1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-nonadecylcyclohexyl)ethyl]cyclohexane

The diamino compound (1) of the present invention can be prepared according to the following steps, and the diol compound (3) and the dinitro compound (2) of the present invention are each intermediates for the compound (1): Hydrogenation

In the above steps, (1), (2) and (3) represent the above formulas, respectively, and the radicals R₁ to R₆ and R₇ to R₁₄ have the above meanings.

The preparation of the diamino compound according to the invention is now described in detail: (First stage)

A 4-[2-(trans-4-alkylcyclohexyl)ethyl]cyclohexanone or a derivative thereof (a) and phenol or a derivative thereof (b) such as o-cresol, m-cresol or 2,6-dimethylphenol are reacted using concentrated hydrochloric acid in the absence of any solvent or in the presence of a suitable solvent such as toluene or xylene at 0° to 70°C, preferably at 10° to 40°C to form a diol compound (3).

(Second step)

The diol compound (3) and p-chloronitrobenzene or a derivative thereof (c) such as 5-chloro-2-nitrotoluene are condensed using KOH or NaOH in a solvent, dimethyl sulfoxide (hereinafter abbreviated "DMSO"), at 40º to 80ºC to form a dinitro compound (2).

(Third step)

The dinitro compound (2) is subjected to catalytic dehydrogenation using a catalyst, palladium-carbon (hereinafter abbreviated to "Pd-C"), in a solvent such as toluene, xylene, benzene, ethanol or methanol at 300 to 80°C to form a diamino compound (1).

As shown in the above reaction steps, it is possible to produce various diol compounds by appropriately selecting the substituents R₁ to R₆ and R₇ to R₁₀ in the first step, and also to produce various dinitro compounds and diamino compounds by appropriately selecting the substituents R₁₁ to R₁₄ in the second step.

(Example)

The preparation of the compounds of the invention is explained in detail below, as are the results of using the resulting polyimide resins in the formation of liquid crystal alignment films.

example 1 (First stage)

4-[2-trans-4-n-pentylcyclohexyl)ethyl]cyclohexanone (112.4 g), phenol (152.7 g) and calcium chloride (90.1 g) were mixed, then concentrated hydrochloric acid (68 ml) was gradually added dropwise with vigorous stirring at room temperature, after which the mixture was stirred for a further 30 minutes, after which the mixture was left to stand at room temperature for 24 hours, then hot water (0.5 l) and ethyl acetate (2 l) were added and the whole was dissolved with heating, washed with a saturated aqueous NaCl solution using water at 40º to 50ºC, dried over Na₂SO₄ dried, filtered, concentrated and the resulting concentrate was recrystallized from a mixed solvent of ethyl alcohol and methyl alcohol (87:13) (SOLMIX manufactured by Nihon Kasei Co., Ltd.) to obtain white crystals of 1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane (78.8 g) as the diol compound of the present invention. Melting point 203.4 - 204.4°C.

(Second step)

To the 1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane (48.8 g) obtained in the first step were added DNSO (300 ml) and KOH (14.7 g), after which the mixture was dissolved with heating to 65°C, a solution of p-chloronitrobenzene (30.8 g) in DMSO (100 ml) was added dropwise at 65°C to react with the mixture, the reaction was allowed to stand for 5 hours, then after completion of the reaction, cooled to room temperature, extracted with dichloromethane, washed with 1N-HCl, then washed with 1N-NaOH aqueous solution, further washed with saturated aqueous NaCl solution until the washing solution was neutral, dried over MgSO₄, chromatographed on an alumina column and the eluate was distilled off, and finally the resulting concentrate was recrystallized from toluene to obtain pale yellow crystals of 1,1-bis[4-(4-nitrophenoxy)phenyl]-4-[2-trans-4-n-pentylcyclohexyl)ethyl]cyclohexane (57.0 g) as the dinitro compound of the present invention. Melting point: 160.5 - 163.0 °C.

(Third step)

1,1-bis[4-(4-nitrophenoxy)phenyl-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane (25.8 g) obtained in the second step was dissolved in a mixed solvent of toluene (200 mL) and SOLMIX (60 mL), after which Pd-C catalyst (Pd content: 5%, water content: 55.9%) (1.5 g) was added, the mixture was cooled with water under atmospheric pressure, contacted with hydrogen gas while stirring, the catalyst was filtered off after the completion of the reaction, the resulting solution was concentrated, and the concentrate was recrystallized from a mixed solvent of toluene and SOLMIX, whereby 1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane (10.5 g) was obtained as a diamino compound of the present invention. Melting point: 170.7 - 171.9°C.

Example 2

Example 1 was repeated, but replacing 4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexanone with 4-[2-(trans-4-n-heptylcyclohexyl)ethyl]cyclohexanone.

In the first step, white crystals of 1,1-bis(4-hydroxyphenyl)-4-[2-(trans-4-n-heptylcyclohexyl)ethyl]cyclohexanone were obtained. Melting point 188.7 - 189.6°C.

In the second step, pale yellow crystals of 1,1- bis[4-(4-nitrophenoxy)phenyl]-4-[2-trans-4-n-heptylcyclohexyl)ethyl]cyclohexane were obtained. Melting point: 129.3 - 130.3 °C.

In the third step, brownish crystals of a diamino compound, 1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2- (trans-4-n-heptylcyclohexyl)ethyl]cyclohexane, were obtained.

Melting point: 167.7 to 168.3ºC.

Application example 1

Into a 200 ml four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen purifier, dehydrated, purified N-methyl-2-pyrrolidone (60 ml) and then 1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-n-pentylcyclohexyl)ethyl]cyclohexane (10.43 g) were added, dissolved with stirring, the solution was cooled to 13°C and pyromellitic dianhydride (4.12 g) was added all at once, the mixture was reacted with stirring and cooling, after 1 hour p-aminophenyltrimethoxysilane (0.91 g) was added, the mixture was reacted with stirring at 20°C for 1 hour and the reaction solution was treated with N-methyl-2-pyrrolidone (NMP) (75 ml) to obtain a transparent 10 wt% solution of a polyamide. This solution had a viscosity at 25°C of 155 cP as measured at 25 ± 0.1°C by means of a type E viscometer (manufactured by Tokyo Keiki Co., Ltd.). The solution was diluted with a solution obtained by mixing butyl cellosolve with N-methyl-2-pyrrolidone (1:1) to form a 3 wt% solution, after which the solution was coated on a transparent glass substrate provided with a transparent ITO (indium oxide-tin oxide) electrode on one side of the substrate by a spin coating method (spinner method) under rotation conditions of 2500 rpm and 20 seconds; the resulting substrate was dried at 100ºC for 10 minutes, subjected to heat treatment at 200ºC in an oven for 90 minutes, after which a polyetherimide film with a coating thickness of about 700 Å was obtained.

The coated surfaces of two substrates with the polyethermide film formed thereon were each subjected to a rubbing treatment to obtain a liquid crystal alignment film, after which a liquid crystal cell having a cell thickness of 20 µm was constructed so that the two liquid crystal alignment films were arranged parallel to the rubbing direction and opposite to each other; then, liquid crystal ZLI-1132 from Merck Co., Ltd. was filled into the cell, the resulting cell was heated to the temperature of an isotropic liquid and gradually cooled until a liquid crystal element was obtained. This element had superior alignment properties and had a pretilt angle of 20° calculated by measuring its electric capacitance.

Application example 2

Application Example 1 was repeated except that the 1,1-bis[4-(4-aminophenoxy)phenyl]-4-[2-trans-4-n-pentylcyclohexyl)ethyl]cyclohexane used in Application Example 1 was replaced by 1,1-bis[4-(4-aminophenoxy)phenyl)-4-[2-(trans-4-n-heptylcyclohexyl)ethyl]cyclohexane, to obtain a 10 wt.% solution of a polyamide having a viscosity of 145 cP. This solution was diluted and used for coating in the same manner as in Application Example 1 and heat-treated to obtain a polyetherimide film having a film thickness of about 1100 Å.

Two of the substrates each having the polyetherimide film formed thereon were converted into a substrate having a liquid crystal alignment film in the same manner as in Application Example 1, thereby obtaining a liquid crystal element having a cell thickness of 20 µm. Liquid crystal ZLI-1132 from Merck Co., Ltd. was filled in the liquid crystal element. The resulting cell exhibited superior alignment properties. The liquid crystal element had a pretilt angle of 15.3º.

Comparison example for the application

2,2-bis[4-aminophenoxy)phenyl]propane (24.92 g), pyromellitic anhydride (15.16 g) and p-aminophenyltrimethoxysilane (3.36 g) were polymerized at 5° to 10°C using N-methyl-2-pyrrolidone (380.3 ml) as a solvent to obtain a polyamide solution (10 wt%, η20 = 113 cP), after which the solution was diluted with a mixture of N-methyl-2-pyrrolidone (1 part) and butyl cellosolve (1 part) to a solution having a concentration of 3%, followed by a spin coating method (spinner method) under the conditions of 3000 rpm. for 20 seconds, preheated at 100°C for 10 minutes, and heat-treated at 200°C for one hour to obtain a polyetherimide film having a film thickness of about 600 Å, which was then subjected to a rubbing treatment to form a liquid crystal cell having a pretilt angle of 5°.

As is clear from the above results, it is possible to obtain a large tilt angle when a 1,1- bis[4-(4-aminophenoxy)phenyl]-4-[2-(trans-4-alkylcyclohexyl)ethyl]cyclohexane is used as a raw material for alignment films. When the length of the alkyl chain bonded to the cyclohexane in the raw materials is increased, it is possible to increase the tilt angle, and when an appropriate alkyl chain length is selected, it is possible to obtain an optimal pretilt angle necessary for the production of liquid crystal elements.

(Effectiveness of the invention)

The diamino compound of the present invention and the dinitro compound and the diol compound as their intermediates are new compounds which were previously unknown. Using the diamino compound as a starting material allow the realization of a large pretilt angle required for STN liquid crystal display elements by conventional rubbing treatment. This is believed to be due to the cyclohexane ring of the diamino compound used as a starting material and the alkyl group bonded to the ring. While the diamino compound of the present invention having this special property was developed mainly with the aim of serving as a starting material and intermediate for organic alignment films for STN cells, the diamino compound is also useful as a high molecular compound such as other polyimides, polyamides, etc. and for their modification, as well as for other purposes such as crosslinkable epoxy resins, etc., and the introduction of new specific properties into high molecular compounds can be expected with its help.

Claims (3)

1. Compounds of the formula wherein R₁, R₂, R₃, R₄, R₅ and R₆ are the same or different and each represents a hydrogen atom or a C₁-C₂₂ alkyl group; R₇, R₈, R₆, R₁₀, R₁₇, R₁₄, R₁₇, R₁₄ and R₁₄ are the same or different and each represents a hydrogen atom or a C₁-C₃ alkyl group; and Y represents NH₂ or a nitro group. 2. Compounds according to claim 1, wherein the groups Y are NH₂ groups. 3. Diol compounds of the formula wherein R₁-R₁₀ have the meanings given in claim 1.